- Email: [email protected]
Electronic properties of epitaxial 6H silicon carbide
Vol. 19, No. 9
ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS
gzz = 2.002 -+0.010,gxx = 1.990 + 0.010, b ° = 2.011 + 0.025, b~ = -- 1.650 + 0.025 GHz. (The K-band values are found to be consistent with the X-band values). From the angular dependence of the data in the ZX plane (i) the angle ×o, which the Z axis makes with the a vector of the unit cell, is determined to be 58.00 + 0.25 ° and (ii) the existence of pseudo-symmetry axes at +- 5° from the Z axis in the ZX plane as found by heat capacity and specific heat data has been confirmed. An estimate is also made of the extent of admixture of the e x c i t e d 6p7/2 state with the ground state ~$7/2.
valley-orbit interaction was taken into account. The electron scattering mechanisms in the epitaxial layers were analyzed and it was shown that the dominant mechanism limiting electron mobility at high temperatures is inter-valley scattering and at low temperatures (20OK), impurity and space charge scattering. A value of 360 cm2/V sec was calculated for the maximum room temperature Hall mobility expected for electrons in pure 6H SiC. The effect of epitaxial growth temperature on room temperature Hall mobility was also investigated.
Received 21 July 1975 Revised 22 March 1976
Received 10 February 1976 Revised 9 April 1976 20. 18.
DEFECTS IN PURE AND HALOGEN COMPENSATED CADMIUM TELLURIDE GROWN BY THE THM METHOD
Received 22 January 1976 19.
ELECTRONIC PROPERTIES OF EPITAXIAL 6H SILICON CARBIDE B.W. Wessels and H.C. Gatos, Massachusetts Institute of Technology, Cambridge, MA 02139, U.S.A.
The electrical conductivity and Hall coefficient were measured in the temperature range from 78 to 900K for n-type epitaxially grown 6H silicon carbide. A manyvalley model of the conduction band was used in the analysis of electron concentration as a function of temperature. From this analysis, the density of states mass to the free electron mass ratio per ellipsoid was calculated to be 0.45. It was estimated that the constant energy surface of the conduction band consists of three ellipsoids. The ionization energy of the shallowest
THE DIFFUSIVE MOTION OF SILVER IONS IN a-AgI: RESULTS FROM QUASIELASTIC NEUTRON SCATTERING G. Eckold and K. Funke, Institut fiir Physikalische Chemie, Universitat G6ttingen and Sonderforschungsbereich 126, Germany; J. Kalus, Physik-Department, Technische Universit~it Mtinchen, Germany; and R.E. Lechner, Institut Laue-Langevin, 156X Centre de Tri, 38042 Grenoble Cedex, France.
R. Stuck, A. Cornet, C. Scharager and P. Siffert, Centre de Recherches Nucl~aires et Universit6 Louis Pasteur, Laboratoire de Physique des Rayonnements et d'Electronique Nucl~aire, 67037 Strasbourg Cedex, France. A theoretical model is proposed which allows the calculation of the concentration of defects in pure and halogen compensated cadmium telluride grown by the THM method. All association and ionization reactions are described in terms of the law of mass action. The ionization energies of the defects are taken from the energy level diagram established by taking into account the latest experimental data. The results indicate that the growth of high resistivity (~ lOS~2-cm) crystals without any compensation is possible in principle. The concentrations of the different defects calculated for chlorine doped material are in good agreement with that measured using a time of flight method.
ix
The diffusive motion of silver ions in a-AgI at 250°C has been studied by quasielastic cold neutron scattering. Spectra were taken in the range of wavevector transfer 0.5 < Q < 2.2 A-1 for elastic scattering. The quasielastic line shapes contain a nrrow and a broad component. They are compared to model calculations allowing for the superposition of two kinds of motion on two different time scales, a local random motion and a translational motion of the jump-diffusion type. The model closely fits the data. The local random motion takes place on a time scale of the order of 10-12sec, with amplitudes of the order of 1 A. It is probably caused by rapid fluctuations of the local potentials due to the diffusive motion of the other cations. The translational motion results in a mean displacement of the silver ion over a distance of the order of a lattice constant (5 A) with a correlation time of the order of 10-11sec. This correlation time is composed of a residence time and a time-of-flight, which are both of comparable magnitude.
Received 23 January 1976 21.
EPR OF M N 4÷ IN LiF : U, Mn V. Lupei and I. Voicu, Institute for Atomic Physics, Bucharest, Romania.
A new manganese center in LiF single crystals doped with U308 and MnO2 has been observed at room and liquid nitrogen temperatures. The trigonal EPR spectrum consists of one very anisotropic fine structure transition with six well-resolved hyperfine components. An
ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS
gzz = 2.002 -+0.010,gxx = 1.990 + 0.010, b ° = 2.011 + 0.025, b~ = -- 1.650 + 0.025 GHz. (The K-band values are found to be consistent with the X-band values). From the angular dependence of the data in the ZX plane (i) the angle ×o, which the Z axis makes with the a vector of the unit cell, is determined to be 58.00 + 0.25 ° and (ii) the existence of pseudo-symmetry axes at +- 5° from the Z axis in the ZX plane as found by heat capacity and specific heat data has been confirmed. An estimate is also made of the extent of admixture of the e x c i t e d 6p7/2 state with the ground state ~$7/2.
valley-orbit interaction was taken into account. The electron scattering mechanisms in the epitaxial layers were analyzed and it was shown that the dominant mechanism limiting electron mobility at high temperatures is inter-valley scattering and at low temperatures (20OK), impurity and space charge scattering. A value of 360 cm2/V sec was calculated for the maximum room temperature Hall mobility expected for electrons in pure 6H SiC. The effect of epitaxial growth temperature on room temperature Hall mobility was also investigated.
Received 21 July 1975 Revised 22 March 1976
Received 10 February 1976 Revised 9 April 1976 20. 18.
DEFECTS IN PURE AND HALOGEN COMPENSATED CADMIUM TELLURIDE GROWN BY THE THM METHOD
Received 22 January 1976 19.
ELECTRONIC PROPERTIES OF EPITAXIAL 6H SILICON CARBIDE B.W. Wessels and H.C. Gatos, Massachusetts Institute of Technology, Cambridge, MA 02139, U.S.A.
The electrical conductivity and Hall coefficient were measured in the temperature range from 78 to 900K for n-type epitaxially grown 6H silicon carbide. A manyvalley model of the conduction band was used in the analysis of electron concentration as a function of temperature. From this analysis, the density of states mass to the free electron mass ratio per ellipsoid was calculated to be 0.45. It was estimated that the constant energy surface of the conduction band consists of three ellipsoids. The ionization energy of the shallowest
THE DIFFUSIVE MOTION OF SILVER IONS IN a-AgI: RESULTS FROM QUASIELASTIC NEUTRON SCATTERING G. Eckold and K. Funke, Institut fiir Physikalische Chemie, Universitat G6ttingen and Sonderforschungsbereich 126, Germany; J. Kalus, Physik-Department, Technische Universit~it Mtinchen, Germany; and R.E. Lechner, Institut Laue-Langevin, 156X Centre de Tri, 38042 Grenoble Cedex, France.
R. Stuck, A. Cornet, C. Scharager and P. Siffert, Centre de Recherches Nucl~aires et Universit6 Louis Pasteur, Laboratoire de Physique des Rayonnements et d'Electronique Nucl~aire, 67037 Strasbourg Cedex, France. A theoretical model is proposed which allows the calculation of the concentration of defects in pure and halogen compensated cadmium telluride grown by the THM method. All association and ionization reactions are described in terms of the law of mass action. The ionization energies of the defects are taken from the energy level diagram established by taking into account the latest experimental data. The results indicate that the growth of high resistivity (~ lOS~2-cm) crystals without any compensation is possible in principle. The concentrations of the different defects calculated for chlorine doped material are in good agreement with that measured using a time of flight method.
ix
The diffusive motion of silver ions in a-AgI at 250°C has been studied by quasielastic cold neutron scattering. Spectra were taken in the range of wavevector transfer 0.5 < Q < 2.2 A-1 for elastic scattering. The quasielastic line shapes contain a nrrow and a broad component. They are compared to model calculations allowing for the superposition of two kinds of motion on two different time scales, a local random motion and a translational motion of the jump-diffusion type. The model closely fits the data. The local random motion takes place on a time scale of the order of 10-12sec, with amplitudes of the order of 1 A. It is probably caused by rapid fluctuations of the local potentials due to the diffusive motion of the other cations. The translational motion results in a mean displacement of the silver ion over a distance of the order of a lattice constant (5 A) with a correlation time of the order of 10-11sec. This correlation time is composed of a residence time and a time-of-flight, which are both of comparable magnitude.
Received 23 January 1976 21.
EPR OF M N 4÷ IN LiF : U, Mn V. Lupei and I. Voicu, Institute for Atomic Physics, Bucharest, Romania.
A new manganese center in LiF single crystals doped with U308 and MnO2 has been observed at room and liquid nitrogen temperatures. The trigonal EPR spectrum consists of one very anisotropic fine structure transition with six well-resolved hyperfine components. An